1. Field of the Invention
The invention relates to hub structures for wheels and particularly to the lubrication of bearings in such hub structures.
2. Description of the Prior Art
A prior art dual wheel hub structure indicated generally at 10 in FIG. 4 is rotatably mounted on an axle 12 and has a radially outward extending flange secured to a brake drum 14, an inner wheel 16 and an outer wheel 18 by bolts 17 and nuts 19. The hub structure 10 includes a hub housing 20, a bearing indicated generally at 22 between a cylindrical secton 24' of the axle 12 and an inside cylindrical bearing surface 26 of the housing 20 adjacent the inner end of the housing, and an outer bearing indicated generally at 24 between a cylindrical section 28 of the axle 12 and an inside cylindrical bearing surface 30 of the hub housing 20 adjacent its outer end. Inner annular lips 32 and 34 of the housing 20 engage the inward facing edges of the outside races of the respective bearings 22 and 24 to maintain their axial spacing, and a shoulder 36 on the axle 12 and a nut arrangement indicated generally at 38 secured on the end of the axle engage the outer edges of the inside races of the respective bearings 22 and 24 to secure the hub structure 10 on the axle 12. The inner bearing 22 and the inner section 24 of the axle 12 have larger diameters than the diameters of the outer bearing 24 and the axle section 28 to facilitate the assembly and disassembly of the hub structure. Between the lips 32 and 34 as well as between the bearings 22 and 24, an inner surface 40 of the hub housing 20 is formed or recessed radially outward relative to the bearing surfaces 26 and 30 and is tapered inwardly from the inner end portion of the hub housing 20 to the outer end thereof. The surface 40 forms an annular lubricant chamber or reservoir 42 which has its greatest depth or diameter adjacent the lip 32 and the bearing 22 for containing oil or lubricant 44 (shown as a toroid in FIG. 4 produced by centrifugal force in the bottom or outer periphery of the annular chamber 42 during high speed rotation of the hub structure 10). Additionally, conventional sealing means (not shown) are provided for sealing the inner and outer ends of the hub structure 10.
Due to leakage and the difference in the diameters of the bearings 22 and 24, the oil level within the chamber 42 is often reduced to a level where the outer bearing 24 receives no lubricant during wheel rotation even though the inner bearing 22 may be adequately lubricated; and thus in the absence of constant replenishment of the lubricant 44, the outer bearing 24 tends to become dry and to fail which can result in more serious consequences than just failure of the bearing.
U.S. Pat. No. 1,234,080 discloses a wheel hub with spiral flanges within a lubricant chamber to provide a positive feed of the lubricant, while U.S. Pat. No. 3,425,760 discloses a wheel assembly with radial vanes on a spacer element surrounding the axle for agitating and aiding in distribution of a lubricant. U.S. Pat. No. 2,474,283 shows a wheel mounting for a brake drum and dual wheels on a trailer, truck or the like. U.S. Pat. No. 2,052,897 shows an arrangement for lubricant distribution including a plurality of relatively short conduits.
Additionally, various other lubrication systems for bearings in various apparatus such as electric motors and turbine motors are illustrated in U.S. Pat. Nos. 3,090,656, 3,111,195, and 3,325,232; the U.S. Pat. No. 3,111,195 showing a stationary pipe for scooping lubricant from an annular sump chamber rotated with a shaft. However, such lubrication systems are generally too complex, too costly or otherwise unsuitable for hub structures such as those employed in dual truck or trailer wheel assemblies.